Visiting high schoolers get a lesson in ‘tree thinking’ from Dr. Pires
June 3, 2013
“What biological concept do flu shots, research on mice, and plant breeding all have in common?” asked Chris Pires of a group of high school students gathered in front of him.
After a moment of silence, he adds, “It starts with an E.”
“Epigenetics,” rang out the students in unison.
“Okay, you’re all way too advanced,” laughed Pires. “Actually, the answer I was looking for is Evolution.”
Advanced is correct. The students were juniors and seniors from Carol Robertson’s and Kevin Grate’s honors genetics class at Fulton High School. The class was visiting with Pires, associate professor of biological sciences, as part of their tour of the Christopher S. Bond Life Sciences Center on May 7.
Although these honors students have already tackled everything from Mendelian genetics to gene regulation, Pires focused on a basic concept of evolution that is often misunderstood by many: phylogenetic trees.
A phylogenetic tree is a graphical representation used in biology to show the evolutionary links between different species and organisms. Like twigs on a tree can be traced back to common branches, a phylogenetic tree shows how species can be traced back to common ancestors.
“Just as reading maps is central to geography, reading and interpreting phylogenetic trees is central to biology,” says Pires. “Yet phylogenetic ‘tree thinking’ remains an overlooked part of both high school and college curriculum.”
Pires and Sarah Unruh, a recently graduated alum of the Division of Biological Sciences, demonstrated the basics of “tree thinking” using pipe cleaners. The students were each given five differently colored pipe cleaners, which they twisted and bent together to form a phylogenetic tree. Each color represented a different species and lineage.
Once constructed, Pires and Unruh peppered the students with questions about their trees, such as “Is the blue species more related to the purple species or to the orange species? Why?” Then, after bending the “branches” to change the configuration of the colors, the students were asked if the relationships between the species changed. The goal of the exercise was to get students to focus on where the branches intersect (the ‘nodes’) rather than on the tips.
“The pipe cleaners give them something to physically touch,” Pires says of the exercise. “Some students do not visualize things well in their mind, and the pipe cleaners give them a grounded experience – and they are colorful and fun.”
The students agree. “Thanks for finding such a fun way to teach phylogenetics to us. It’s so much better to learn with fun,” commented one of the students in a follow-up note to Pires.
The high school students’ visit to the Bond Life Sciences Center also included tours of the DNA Core and Charles W. Gehrke Proteomics Center. Beverly DaGue, a senior research chemist for the proteomics center and the Division of Biological Sciences, provided the students with results from a mass spectrometry analysis of a protein isolated by the students as part of a year-long genetic experiment with plants.
The pipe cleaner phylogeny method was developed by Kristy Halverson, an alumnus of both MU and Fulton High School. Halverson is now a faculty member at the University of Southern Mississippi in Hattiesburg. The technique is described in The American Biology Teacher 72(4):223-224.
Written by: Melody Kroll
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